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Home , Acer macrophyllum, Acer saccharum, Acleris chalybeana, Cornus alternifolia, Eutypella parasitica, Maple sugar

Marsh.

Aceraceae Maple family Richard M. Godman, Harry W. Yawney, and Carl H. Tubbs

Sugar maple (Acer saccharum), sometimes called in temperatures are from 40” C (40” F) in the hard maple or rock maple, is one of the largest and north to 38” C (100” F) in the southwestern areas. more important of the . It grows on ap- Occasional extremes may be more than 11” C (20” F) proximately 12.5 million hectares (31 million acres) lower or higher than these. or 9 percent of the land and has a net Precipitation averages range from about 510 mm volume of about 130 million m3 (26 billion fbm) or 6 (20 in) annually near the western edge of the range percent of the hardwood sawtimber volume in the to 2030 mm (80 in) in the southern Appalachians. United States. The greatest commercial volumes are Much of the northeastern region receives about 1270 presently in Michigan, , , , mm (50 in) per year where substantial commercial and (53). In most regions, both the volumes of sugar maple are located. In general, the sawtimber and growing stock volumes are increas- growing season precipitation is well distributed and ing, with increased production of saw logs, pulpwood, averages 380 mm (15 in) in the western areas and and more recently, firewood. 1020 mm (40 in) in the East. Snowfall often exceeds 2540 mm (100 in) in the northern portion of the range. Habitat In the broad geographic area covered by sugar maple, the growing season ranges from 80 to 260 Native Range days. The last killing frost usually occurs from March 20 to June 15 and the first killing frost occurs The northern limit of sugar maple (figs. 1, 2) near- between September 1 and November 10. In moun- ly parallels the 35th mean annual isotherm extend- tainous areas of the Northeast, climatic factors large- ing eastward from the extreme southeast corner of ly determine the upper elevation limits of the Manitoba, through central Ontario, the southern (97). third of and all of New Brunswick and Nova Scotia. Within the United States the species is found Soils and Topography throughout New England, New York, Pennsylvania, and the middle Atlantic States, extending south- westward through central to the Ap- Sugar maple grows on a wide variety of sites rang- palachian Mountains, then southward through the ing from a site index of about 12 m (40 ft) to nearly western edge of to the southern bor- 24 m (80 ft) at age 50 (12,17,21,25,46,91). Typical der of . The western limit extends through good quality second-growth stands usually fall be- into a small area of Kansas, the eastern tween site index 17 and 20 m (55 and 65 ft) for sugar one-third of Iowa, and the eastern two-thirds of Min- maple at base age 50 years. Height growth is slower nesota. A few outlier communites are found in north- after age 50 in the eastern regions. Except on the ern Kansas, Georgia, and the Carolinas. best sites, the depth of the soil and type of parent material has a marked influence on site index (69). Climate Sugar maple grows on sands, loamy sands, sandy loams, loams, and silt loams but it does best on well-drained loams (30). It does not grow well on dry, Sugar maple is restricted to regions with cool, moist climates. In northern areas, January tempera- shallow soils and is rarely, if ever, found in swamps tures average about -18” C (0’ F) and July tempera- (30). Sugar maple is soil-site specific in southerly regions but abundant on a wide variety of soils in the tures about 16” C (60” F). In the southern portions northern Lake States. It is mostly found on of the range, January temperatures average about Spodosols, Alfisols, and Mollisols among the soil or- 10” C (50” F) and July temperatures approach 27” C ders. In , sugar maple is associated (80” F), although moisture and aspect influence these with sites that have abundant organic matter (69), extremes. In the sugar maple region, typical ranges and in West it is most abundant on areas with high site indices (107). The authors are Principal Silviculturist (deceased), North Central Sugar maple grows on soils ranging from strongly Forest Experiment Station, St. Paul, MN, and Research acid (pH 3.7) to slightly alkaline (pH 7.3), but it most Foresters, Northeastern Forest Experiment Station, Radnor, commonly grows on soils with a pH of from 5.5 to 7.3 PA. (30). The heavy litter typical of sugar maple

78 Acer saccharum

tends to modify the pH and nutrient status of the pH range of 4.5 to 7.0 but drops as the soils become soil. The contain about 1.81 percent calcium, more acid (5). 0.24 percent magnesium, 0.75 percent potassium, In the Lake States, sugar maple is found at eleva- 0.11 percent phosphorus, 0.67 percent nitrogen, and tions up to 490 m (1,600 ft)-most commonly on 11.85 percent ash, based on dry weight. The pH of ridges between poorly drained areas and on soil with leaves ranges from 4.0 to 4.9. The calcium content at least 1 to 1.5 m (3 to 5 ft) to the water table. In remains relatively uniform in growing with a northern New England and New York State it grows at elevations up to 760 m (2,500 ft.). In the Green

Figure l-The native range of sugar maple.

79 Acer saccharum

Mountains of and the White Mountains of Associated Forest Cover New Hampshire, especially, the upper limit lies in a sharp horizontal band with a narrow transitional In eastern sugar maple is a major zone into the Boreal forest types. In the southern component in 7 Society of American Foresters forest Appalachians the upper elevation ranges from 910 m cover types, a common associate in 17, and an infre- (3,000 ft) to 1680 m (5,500 ft), with the lower levels quent species in 10 (20). generally restricted to the cooler north slopes. In the Sugar maple is a major component in the following southern and southwestern parts of its range, sugar types: maple more typically grows on moist flats and along ravines at intermediate elevations in the rolling 27 Sugar Maple topography. 26 Sugar Maple-Basswood 25 Sugar Maple--Yellow 60 Beech-Sugar Maple 28 Black Cherry-Maple 31 Red Spruce-Sugar Maple-Beech 16 Aspen (Canadian subtype)

Sugar maple is a common associate in the follow- ing types:

17 Pin Cherry 107 White Spruce 32 Red Spruce 30 Red Sprucr+Yellow Birch 35 Paper Birch-Red Spruce-Balsam Fir 21 Eastern White Pine 22 White Pine-Hemlock 23 Eastern Hemlock 20 White Pine-Northern Red Oak-Red Maple 24 Hemlock-Yellow Birch 108 Red Maple 19 Gray Birch-Red Maple 55 Northern Red Oak 57 Yellow-Poplar 58 Yellow-Poplar-Eastern Hemlock 59 Yellow-Poplar-White Oak-Northern Red Oak 64 -Persimmon

It occurs as an infrequent species in Jack Pine (Type 11, Balsam Fir (Type 51, Aspen (Type 16), Red Spruce-Balsam Fir (Type 33), Red Spruce- (Type.34), Chestnut Oak (Type 441, Pine (Type 45), White Pine-Chestnut Oak (Type 511, White Oak-Black Oak-Northern Red Oak (Type 52), and River Birch-Sycamore (Type 61). Large numbers of shrubs are found with sugar maple because of its varied altitudinal distribution. The most common within the commercial range are beaked (Corylus cornuta), Atlantic leatherwood (Dirca palustris), redberry elder (Sambucus pubens), American elder (S. canadensis), alternate-leaf dog- ( alternifolia), dwarf bush-honeysuckle (Diervilla lonicera), yew (Taxus canadensis), red raspberry (Rubus idaeus), and blackberries (Rubus spp.). Common flowering include springbeauty (Claytonia caroliniana), large-flowered trillium (lWlium grandiflorum), anemone (Anemone Figure Z-Sugar maple. spp.), marsh blue violet (Viola cucullata), downy yel-

80 Acer saccharum

low violet (I? pubescens), Solomons-seal 20,07O/kg (3,200 to 9,10O/lb) (85). The large papery (Polygonatum pubescens), false Solomons-seal wings, typically 20 to 27 mm (0.8 to 1.1 in) in length (Smilacina stellata), sweet cicely (Osmorhiza spp.), and 7 to 11 mm (0.3 to 0.4 in> wide, permit the adderstongue (Ophioglossom vulgatum), jack-in-the- samara to be carried at least 100 m (330 ft) by the pulpit (Arisaema atrorubens), clubmosses wind. During a good year in northern Michigan, (Lycopodium spp.), and largeleaf aster (Aster macro- 173,000 samaras per hectare (70,00O/acre) fell in the phyllus). center of a 4-ha (lo-acre) clearcut (31). Samaras con- taining seed can be readily separated from empty Life History samaras by immersion in N-pentane. Immersion up to 1 hour may delay germination but has no effect on Reproduction and Early Growth seed viability (124). Light crops are produced by 40- to 60-year-old Flowering and Fruiting-Sugar maple trees sel- trees with 20 cm (8 in) d.b.h., and moderate crops by dom until they are at least 22 years old; 70- to loo-year-old trees with 25 to 36-cm (lo- to flowering is heavier at later ages. The flower buds 14-m) d.b.h. Saw-log-size trees produce vast numbers usually begin to swell at or slightly before the leaf of samaras. During an excellent fruiting year in buds show activity and reach full bloom 1 to 2 weeks northern Michigan, a series of traps caught 22 mil- before leaves emerge. appear between late lion/ha (8.56 million/acre) sugar maple samaras in a March and mid-May, depending on the geographic virgin stand and 11 million/ha (4.3 million/acre) in a location (85). selectively cut stand (30). Flowering in sugar maple is polygamous, occurring Based on 32 years of observation in north-central over the entire crown. The long-pedicelled, apetalous Wisconsin, good or better fruit crops occurred about yellow flowers, about 6.4 cm (2.5 in) long, seem to be 44 percent of the years, the lowest percentage among perfect, but usually only one sex is functional within the major hardwood species of the area (37,401. Good each flower. Both sexes are typically produced in the or better fruit crops occurred as often as 4 successive upper part of the crown but only males form in the years, but successive poor crops did not extend longer lower part (26). In some trees, certain major limbs than 2 years. The period between good or better produce only male and others only female flowers. crops ranges from 1 to 4 years in north-central Wis- The flowers of sugar maple were thought to be bee- consin, from 2 to 5 years in other portions of the pollinated (30,641, but a recent study showed that United States, and from 3 to 7 years in Canada pollination occurs freely in sugar maple without the (30,47,115). aid of (28). To germinate, sugar maple require moist The fruit, a double samara, ripens in about 16 stratification at temperatures slightly above freezing weeks. Usually only one of the paired samaras is for 35 to 90 days. Each sugar maple seed seems to filled with a single seed, typically averaging 7 to 9 have its own stratification-period threshold, short of mm (0.3 to 0.4 in) in length, but occasionally both which the epigeal germination process ceases (126). samaras will contain seed or both will be empty. Both moisture content and temperature affect how Some trees produce triple samaras and others long seeds can be stored. Under proper conditions produce samaras with double wings. Samaras col- seeds have been stored for at least 5 years without lected from trees having the birds-eye wood grain loss of viability (10). In natural stands, few if any characteristic showed a consistency of overlapping of seeds remain viable on the forest floor beyond the the wings, a strong union between samaras, and first year (73). lighter colored wings after drying but these charac- Sugar maple seed has an extremely high germina- teristics have not been confirmed as being an at- tion capacity, with averages of 95 percent or more tribute associated with birds-eye (32). (126). The optimum temperature for germination is Seeds are mature when the samaras turn yel- about 1” C (34” F), the lowest of any known forest lowish green and have a moisture content less than species (39,108). Germination drops rapidly as 145 percent (11,124). The samaras begin falling temperatures increase, and little if any germination about 2 weeks after they ripen, usually just before occurs above 10” C (50” F). Rapid warming of the the leaves fall. surface soil in the spring of 1978 in northern Wiscon- sin, for example, prevented germination from the Seed Production and Dissemination-The bumper seed crop of 1977, except in a few remaining fruit of sugar maple is intermediate in size among snowbanks along the roads (38). Under natural con- species within the genus. Samaras average about ditions the cotyledon leaves are out and growing 15,40O/kg (7,000/1b), but range from 7,060 to before the snow is gone in the northern regions. This

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unique characteristic of germination at low tempera- per hectare did not differ significantly at either 2 or tures probably accounts for the abundance of sugar 5 years after cutting. After 10 years, seedlings under maple regeneration under most stand conditions in the lightest overstories (6.9 m2/ha or 30 ft’/acre) grew the north. Another major characteristic of the ger- most rapidly although seedlings were abundant minating sugar maple seed is its vigorous develop- under all overstory densities (109). ment of a strong radicle that has the strength and In the drier Lake States region, natural seedlings length to penetrate heavy leaf litter and reach must have overstory shade for survival until they mineral soil during the moist period. reach 0.6 to 1.2 m (2 to 4 ft) in height, at which time their systems have developed from the litter- Seedling Development-Seedlings of sugar mineral soil interface into mineral soil. The entire maple are very shade tolerant and can survive long overstory can then be removed with high seedling periods of suppression. In a study of seedling height survival and full stocking (42). Removing the over- for 5 years after germination under low lath shade story before seedlings are established usually results in central Ontario, the tallest seedlings were found in semipermanent wildlife openings in the Lake under about 65 percent shade, averaging about 127 States (112). In partially cut stands, the tallest seed- cm (50 in) tall (34,71). Heights were greater than 102 lings usually develop and constitute the trees of the cm (40 in) from about 35 to 90 percent of full sun- new stand as the overstory is gradually removed light, with average heights decreasing at more open (78). and heavier shading. A significant finding in this Planting or other special regenerative measures study was that supplemental watering was necessary are rarely needed for sugar maple in New England for survival at more than 55 percent of full sunlight. or the Lake States where the grows naturally. Dry weight and root development were little affected In other regions, sugar maple is less aggressive and by the level of light. A Vermont study of shade levels planting is a desirable practice. Nursery stock used showed no significant difference in seedlings grown in planting is usually fall sown at a depth of about under 0, 30, and 60 percent shade but found a 6 mm (0.25 in) and covered with about 6 mm (0.25 marked decrease in development under 90 percent in) of sawdust. The nursery bed is covered by about shade. Seedlings grown under the different shade 50 percent lath shade. Sowing density should yield treatments showed no difference, however, in either about 130 to 160 seedlings per square meter (12 to height or diameter growth 4 years after field - 15 seedlings/ft2) and seedlings should be vertically ing (125). root pruned before lifting, usually as 2-O stock Sugar maple release an exudate that can (101,121,124). On more difficult sites 3-O stock is inhibit the growth of yellow birch when the root preferred with tops averaging about 25 cm (10 in) or growth periods coincide, thus gaining a growth ad- about twice the height of 2-O seedlings (101). vantage over one of its associated species (110). Open field plantings with sugar maple have a high Other tree species may be similarly affected. Aster survival rate, but seedlings grow poorly because of and goldenrod exert an allelopathic effect on sugar their inability to compete for moisture and nutrients maple by reducing germination and early growth of with herbaceous vegetation. Generally, open field seedlings (24). plantings require good stock and several years of site The growth of understory seedlings begins before maintenance to assure success (114,127). Time of the overstory leafs out, generally about mid-May in planting is important. Survival and growth can be Upper Michigan. About 90 percent of the seasonal vastly improved by planting very early in the spring height growth occurs within 18 days under dense compared to planting late in the spring. The increase stands and 24 days in the open (50). The major is attributed to the greater root regeneration growth of other species studied extended about three capabilities during that time (118). Fall plantings times longer. have been highly successful in Vermont (127). Sugar Seedling numbers greater than 370,50O/ha maple must be planted at relatively close spacings in (150,00O/acre) are common, although as many as 50 order to correct the forking problems that result from percent of the new seedlings may not survive the the frequent loss of the terminal bud in this opposite- first year. Seedlings in the understory of young, branched species (78,89). dense stands may not survive for more than 5 years but many of the seedlings under stands averaging 25 Vegetative Reproduction-Sugar maple cm (10 in) d.b.h. or more will persist, although they reproduces by stump sprouts and will occasionally will have little annual height growth until released. layer (22). Root suckering is rare. Seedlings broken In a study of reproduction in old growth stands cut during logging readily sprout from dormant buds on to various basal area densities, number of seedlings the lower bole and quickly regain the height of un-

82 Acer saccharum

damaged seedlings (52). Initial deformities, primarily sensitive to surface moisture conditions because they crook, and stem losses from deer browsing are rapid- have a shallow, fibrous root system that lies between ly overgrown and corrected without development of the litter-mineral soil interface of typical podzols. internal rot (51). With a gradual increase in light, the root systems In older stands, the percentage of stumps sprout- penetrate deeper into the mineral soil and height ing decreases with increase in tree size, stand den- growth increases. sity, and years since cutting. Two years after a cut- Growth during the pole stage is slower than for ting in northern Michigan, the most sprouting most associated hardwood species. Height and radial occurred on l&cm (6-in) trees and the least sprouting growth begins at about the same time as the buds on 76-cm (30-in) trees. The percent of stumps sprout- leaf out. Height growth is completed in about 15 ing averaged 94 and 38, respectively. Five years after weeks and radial growth in from 14 to 17 weeks, cutting, the percent of sprouting dropped to about 58 depending on the season and locality (30). In some and 6, respectively. The number of sprouts per stump areas, height growth is about 85 percent complete also declined with years since cutting (30). Sugar within 5 weeks and cambial growth is about 80 per- maple is a prolific sprouter in the North, but it cent complete in 8 weeks (30). sprouts less than other hardwood species in the In the Lake States, older sugar maple trees (fig. 3) southern part of its range (9,86,88,99). in a mature stand grew 2.5 cm (1 in) d.b.h. in 10 Cuttings of sugar maple can be rooted but may years (30). Maximum diameter growth rates of in- later fail due to poor overwintering survival. Cut- dividual trees in mature stands in the Upper Penin- tings can be successfully over-wintered by forcing the sula of Michigan were about 7.6 cm (3 in) per decade cutting to break bud and produce a flush of new for 46-cm (18-in) trees, 8.9 cm (3.5 in) for 30-cm growth immediately after it roots with the use of (12-in) trees, and 10.2 cm (4 in) for 15-cm (6-in) trees gibberellic acid (128). Rooting response varies greatly (15). Growth in second-growth stands, however, between clones-differences range from 0 to 100 per- generally exceeds 5.1 cm (2 in) in 10 years for saw- cent, and rooting response tends to be consistent log-size trees (18) and a maximum rate in excess of from year to year. Timing the collection of cuttings is 10.2 cm (4 in) has been reported (106). For the first critical; those taken in mid-June generally give the 30 to 40 years, sugar average about 30 cm best results. A rooting medium consisting of a 1 to 1 (12 in) a year in height growth. mixture of perlite and sphagnum moss, with inter- Mature trees and stands of sugar maple reach 300 mittent misting, has worked well with sugar maple to 400 years of age, 27 to 37 m (90 to 120 ft) in cuttings. The reliability of cuttings to propagate trees height, and 76- to 91-cm (30- to 36-in) in d.b.h. (30). with figured wood, such as curly grain and birds-eye, Following repeated cutting under the uneven-aged has not been verified (30). system, age and diameter show strong linear relation Sugar maple trees with desirable genetic charac- with the older ages, seldom exceeding 250 years teristics can be reproduced by grafting. Success with (68,111). Height growth usually ceases or becomes this method can be highly variable depending to a negligible at about 140 to 150 years (30). Diameter large degree on grafting techniques, that is, when growth continues at a decreasing rate with age and and under what conditions the scions were collected size. The largest reported sugar maple tree, growing and handled, treatment of the rootstock, and ex- near Kitzmiller, MD, has a d.b.h. of 209 cm (82.1 in), perience of the grafters (129). Of the various methods is 23.8 m (78 ft) tall, and has a crown spread of 20.1 available, bud grafting is used most commonly and m (66 ft) (1). with a high degree of success by commercial nur- Yields of mixed hardwood stands, but serymen (64). predominantly sugar maple, range up to a maximum Air-layering, a method of propagation that stimu- of 216 m3/ha (14,000 gross board feet/acre) (30,70). lates root development on branches still attached to Yields for northern hardwood stands in the Lake the parent tree, is another method that has been States are available from estimates of average stand successfully used (16). A major disadvantage of this age and average stand diameter (table 1). Both procedure is that branches on some trees selected for propagation may not be readily accessible. parameters are based on overstory trees. Basal-area stocking of stands commonly ranges from 27.6 to 36.8 m2/ha (120 to 160 ft2/acre). A few older stands exceed Sapling and Pole Stages to Maturity 45.9 m2/ha (200 ft2/acre). Even-age and uneven-age silvicultural systems are available for managing Growth and Yield-Early growth of sugar maple stands in which sugar maple is a principal com- is slow, partly because it regenerates under heavy ponent and a desired species. Periodic annual growth shade. In natural stands, the younger seedlings are averaging about 4.2 m3/ha (350 tbm/acre) and annual

83 Acer saccharum

Table l-Yields from average, well-stocked stands of northern hardwoods in the Lake States dominated by sugar maple (adapted from 29)

Stand Average Basal Volume age W d.b.h. area Total2 Saw log3 cm n?/ha d/ha n&ha Good site 40 19 19.7 92.4 13.3 80 29 26.4 193.9 85.4 120 38 31.5 265.3 150.5 160 47 35.6 317.1 197.4 200 56 38.6 350.0 228.2 Medium site 40 14 18.8 51.8 4.2 80 24 25.0 135.1 49.0 120 31 29.4 202.3 100.8 160 38 32.8 250.6 144.2 200 44 35.6 283.5 176.4 Poor site 40 10 16.3 25.2 1.4 80 19 22.0 72.1 16.8 120 25 25.9 127.4 53.2 160 30 28.7 175.0 86.1 200 35 30.8 211.4 116.2 in W/acre V/acre fbmiacre Good site 40 7.4 86 1,320 950 80 11.6 115 2,770 6,100 120 15.1 137 3,790 10,750 160 18.6 155 4,530 14,100 200 22.1 168 5,000 16,300 Medium site 40 5.6 82 740 300 80 9.5 109 1,930 3,500 120 12.2 128 2,890 7,200 160 14.8 143 3,580 10,300 200 17.4 155 4,050 12,600 Figure 34 mature sugar maple stand in Nicolet National Forest, Poor site WI. 40 4.1 71 360 100 80 7.6 96 1,030 1,200 120 10.0 113 1,820 3,800 basal-area growth of up to 0.7 m2ka (3 ft2/acre) is 160 11.9 125 2,500 6,150 typical of young stands on good sites in the Lake 200 13.8 134 3,020 8,300 States but varies with total basal-area stocking, dis- ‘Age determined from overstory trees. tribution of trees by size class, and site (18). Im- ‘Cubic volumes determined from sound trees 13 cm (5 in) and larger in d.b.h. to a top diameter inside bark of 10 cm (4 in), exclusive of bark. provement in grade and tree size should be the guid- qhe Scribner log rule was used for trees 23 cm (9 in) and larger in d.b.h. to a variable top ing principle in stand management because this diameter, with a minimum of 20 cm (8 in) inside bark. Deductions were made for cull. factor contributes more to value increase than diameter growth under most conditions (41,75,105). remain within the general area of origin (23,103). Intraspecific root grafting is common. Rooting Habit-The root system of sugar maple Although some root growth may continue has strong, oblique laterals with extensive branch- throughout the year if the soil does not freeze, the ing. Roots on the upper side of the laterals grow bulk of the new root regeneration depends on growth upward into the humus layers and those on the lower factors exported from physiologically nondormant side grow downward. Most of the fine feeder roots buds. In northern races of sugar maple, about 2,500

84 Acer saccharum

hours of continuous chilling are required to break pettitana, Phyllobius oblongus, and Platycerus vires- bud dormancy (64). tens (65,66,77,98,123). Sugar maple roots are extremely sensitive to flood- Forking at the terminal bud occurs in trees of all ing during the growing season. The roots of maple ages but is especially pronounced in overstory trees. form both endotrophic and ectotrophic mycorrhizae. Side crowding and overhead shading help correct lower forking (32). But early or heavy thinning sets Reaction to Competition-Sugar maple is rated the fork and causes shorter merchantable lengths. As as very tolerant of shade, exceeded among hardwoods fork members increase in size and weight, fork only by a few smaller, shorter lived species. In large breakage also increases. trees, only American beech () Except for bud losses, sugar maple is not highly equals it in tolerance under forest conditions (30). susceptible to injury and serious outbreaks are Maximum photosynthetic activity generally occurs not common (62). The most common insects to attack under about 25 percent of full sunlight. The species sugar maple are defoliators and these include the can survive for long periods under heavy shade and gypsy (Lymantria dispar), forest tent caterpil- still show a strong response to release (30). lar (Malacosoma disstria), linden looper (Erannis Release is seldom justifiable for young sugar maple tiliaria), fall cankerworm (Alsophila pometaria), stands subjected to suppression from scattered spring cankerworm (Paleacrita vernata), green- dominant trees or pin cherry (Prunus pensylvanica) striped mapleworm (Anisota rubicunda), Bruce span- because the sugar maple will overcome suppression worm (), maple leaf-cutter under those conditions (30). Release is needed, how- (Paraclemensia acerifoliella), maple trumpet ever, when sugar maple competes with striped maple skeletonizer (Epinotia aceriella), and saddled (), black cherry (Prunus serotina), prominent (Heterocampa guttivitta). yellow-poplar (Liriodendron tulipifera), and the One insect of the genus Phytobia occasionally (Quercus spp.), because growth is retarded and sur- causes pith flecks that seriously degrade veneer logs. vival is reduced by such competition (107). This insect tunnels the full length of the cambium One sapling stand study showed that unreleased, layer and exits near the root collar (117). dominant trees of good vigor averaged 23 mm (0.9 in) Borers that attack sugar maple include the car- in diameter growth and heavily released trees penterworm (Prionoxystus robiniae), sugar maple averaged 46 mm (1.8 in) in diameter growth per year borer (Glycobius speciosus), maple callus borer during a 7-year period; unreleased, codominant trees (Synanthedon acerni), and occasionally horntails of good vigor averaged 18 mm (0.7 in) in diameter (‘Xiphydria abdominalis and X. maculata) (95). growth and heavily released trees 38 mm (1.5 in). Sucking insects that affect sugar maple include the Pole-size trees also respond well to release (31,102). woolly alder aphid (Prociphilus tesselatus) and other If released too much, sugar maple readily develops aphid species (Neoprociphilus aceris and Periphyllus epicormic sprouts from dormant buds (14,31,33, lyropictus) which injure leaves and reduce growth. 36,781. Gradual release and good crown development Of the scale insects, the maple phenacoccus provide adequate control over epicormic sprouting (Phenacoccus acericola), is the most important to and also enhance natural pruning of epicormic sugar maple. The maple leaf scale (Pulvinaria branches on the lower bole. Consequently, proper acericola) and the gloomy scale (Melanaspis thinning at scheduled intervals is necessary to en- tenebricosa) also frequently attack sugar maple. courage quality improvement as well as diameter growth. Many sugar maple trees died in a small area of Wisconsin and Michigan in 1957 (113). Certain in- Damaging Agents-Early studies in old-growth sects-the leaf rollers (Sparganothis acerivorana and sugar maple indicated that after two or possibly chalybeana) and the maple webworm three cyclic cuts had been made, few damaging (Tetralopha asperatella)-combined with disease and agents would affect trees or stands. Current work in climatic factors were thought to be the cause of this second-growth, however, shows some major agents, mortality (44,48,61,120). The decline has abated but particularly in even-aged stands (77,122). appears to have recurred with less severity on a At least two species of bud miners, Proteoteras portion of the same area in the late 1970’s. moffatiana and Obrussa ochrefasciella, overwinter in Diseases of sugar maple generally deform, discolor, the terminal bud of sugar maple and kill it. This or decrease volume but seldom kill the tree (80). The causes repeated forking, which reduces merchantable two most important diseases in managed second- log length and adds to the risk of crown loss from growth are probably () splitting. Other bud-damaging insects that may also and Nectria (Nectria galligena) cankers. In the Lake cause forks are Choristoneura rosaceana, Cenopis States these cankers each affect from about 1 to 4

85 Acer saccharum

percent of the trees (77) but in Ontario they occur winter heating of the bole above the snowline on more frequently (60,87). Nectria canker is more bright sunny days followed by rapid freezing that prevalent following shelterwood cuttings, probably ruptures the cells. Most injury occurs when the because conditions favorable for infection are estab- stems are 2.5 to 7.6 cm (1 to 3 in) in d.b.h., and lished (2). Two other cankers (Schizoxylon micro- certain topographic positions are affected more than sporum and Hypoxylon lilakei) occur rarely on sugar others (55). Healing in dense stands is slow, if at all, maple. In a few instances cankers may kill a tree but and later stages often appear to be a simple frost generally only predispose it to breakage. crack. Various fungi may be present but may or may Some common fungi-causing heart rots in sugar not prevent closure (59). Part of the lack of closure maple are Armillaria mellea, primarily a root-rotting may be due to shrinkage and swelling of the bole ; Hydnum septentrionale, which causes a soft, associated with changes in air temperature (35). spongy, white heart rot; Inonotus glomeratus, which In some areas the lower portion of sugar maple causes white to light brown spongy heart rot; and boles contains many vertical cracks from 2.5 to 7.6 Ustulina vulgaris, which causes a butt rot (30). cm (1 to 3 in) long. Although these cracks have been The amount of defect in sugar maple trees in vir- termed annual maple cankers, the causal agent does gin and unmanaged stands is usually high-com- not seem to be a fungus. These cankers slowly dis- monly from 35 to 50 percent (30). Defect resulting appear and new ones recur at short intervals (32). In from logging damage usually is minor in small Pennsylvania they were most common on slowly per- wounds for as long as 10 years, but 20-cm (&in) scars meable soils (116) but no specific cause has been all were infected within 20 years and value losses identified (3,581. were significant (47,811. Sugar maple can be severely damaged from de- Logging injuries to the stems of residual trees and icing road salt (96). In an industrial area the number to reproduction frequently result in the entrance of of overstory sugar maples was markedly reduced decay and eventually serious volume loss (6,79). In a from exposure to sulfur oxides, nitrogen oxides, study in Upper Michigan at least 30 percent of the chlorides, and fluorides. Sugar maple remained an logging scars on the main stem of older trees resulted abundant species in the understory because of a in serious defects within 15 to 20 years (30). Larger lower exposure level (72). limbs broken in logging also usually result in serious Numerous feed on or injure sugar maple defects (93,94). In Upper Michigan after a 20-year without serious effect except in local and limited period about 8 percent cull resulted from decay and situations. Deer browsing is probably the most com- stain that had entered through scars on limbs 10 cm mon wildlife factor. Winter browsing in the Lake (4 in) and larger (30). Smaller limb breakage expos- States causes little damage or reduced growth ing only sapwood, however, generally results in little (51,100). In the central Adirondacks, however, con- volume loss (4,30). tinual browsing of sugar maple allows American Two wilts occasionally attack and kill sugar maple. beech, which the deer avoid, to dominate northern Sapstreak, caused by Ceratocystis coerulenscens, hardwood understories (54). enters through root injuries from logging and has Red, grey, and flying squirrels sometimes gnaw or been reported in several localities (56,57,80). Verticil- feed on the seed, buds, foliage, and twigs of sugar lium wilt, caused by Verticillium albo-atrum, is maple. In rare instances, they have girdled and usually found only in shade trees. This wilt also killed larger branches and tree tops (30,100). Por- invades the trees through the roots. cupines may feed on the bark and kill the top by When stored for more than a year, a saprophytic girdling the upper stem (8,30). fungus, Cryptostroma corticale, sometimes develops Sapsuckers frequently peck and cause degrade in on the bark of sugar maple. The spores from this some sugar maple trees but rarely, if ever, kill the fungus are released during processing and have tree (19,82,90,92). On heavily pecked trees in the caused bronchial asthma and severe allergenic lung spring a fungus develops on the and causes the disorders to millworkers (83,84). bark to turn black (82). Such trees probably should Physical and climatic injuries often occur on sugar be retained in the stand to prevent other trees from maple. Much damage from glaze storms occurred in being attacked. New York in 1942. The injured trees showed a slight tendency to sprout and renew growth. Many of the Special Uses smaller trees that had 85 percent or more of their crown broken away developed saprot (30). The sugar maple tree is the principal source of Winter sunscald frequently occurs in even-aged . The trees are tapped early in the spring sugar maple stands. Trees are damaged from late for the first flow of sap, which usually has the Acer saccharum

highest sugar content. The sap is collected and boiled 3. Barnard, Joseph E., and Wilbur W. Ward. 1965. Low or evaporated to a . Further concentration by temperatures and bole canker of sugar maple. Forest evaporation produces the maple sugar. Sugar maple Science 11(1):59-65. sap averages about 2.5 percent sugar; about 129 4. Basham, J. T., and H. W. Anderson. 1977. Defect liters (34 gal) of sap are required to make 3.8 liters development in second-growth sugar maple in Ontario. I. Microfloral infection relationships associated with dead (1 gal) of syrup or 3.6 kg (8 lb) of sugar. Guides have branches. Canadian Journal of Botany 55(8):934-976. been printed for developing a from 5. Beals, E. W., and J. B. Cope. 1965. Vegetation and soils in natural stands (67). an eastern . Ecology 45(4):777-792. Breeding experiments have determined that sugar 6. Biltonen, Frank E., William A. Hillstrom, Helmuth M. content is high for certain families and that sugar Steinhilb, and Richard M. Godman. 1976. Mechanized content in individual trees is consistent over a period thinning of northern hardwood pole stands: methods and of years (64,104). A sugar content of 7.4 percent has economics. USDA Forest Service, Research Paper NC-137. been attained by crossing two selected parents of North Central Forest Experiment Station, St. Paul, MN. slightly lower content (64). The sugar content is also 17 p. correlated with the volume yield of sap (7,74). 7. Blum, Barton M. 1974. Relation of sap yields to physical characteristics of sugar maple trees. Forest Science 19(3):175-179. 8. Brander, Robert B. 1973. Life history notes on the Genetics porcupine in a hardwood-hemlock forest in Upper Michigan. Michigan Academician 5(4):425-433. Sugar maple is a genetically variable tree. Some 9. Braun, E. Lucy. 1950. forests of eastern North botanists recognize from three to six varieties or America. Hafner Publishing Co., New York. 596 p. forma that differ in morphological characteristics, 10. Carl, Clayton M., Jr. 1976. Effect of separation in N- but others consider them to be subspecies. Extensive pentane on storability of sugar maple seeds. USDA Forest research indicates a “flow of characteristics” over the Service, Research Note NE-218. Northeastern Forest wide geographic distribution and variation in habitat Experiment Station, Upper Darby, PA. 3 p. conditions (30,64). Kriebel indicated that sugar 11. Carl, Clayton M., Jr., and Albert G. Snow. 1971. Maturation maples could be grouped into three major geographic of sugar maple seed. USDA Forest Service, Research Paper races or ecotypes, each containing a parallel clinal NE-217. Northeastern Forest Experiment Station, Upper variation (30). Provenance tests in his study indicate Darby, PA. 9 p. 12. Carmean, Willard H. 1978. Site index curves for northern differences in drought endurance, resistance to leaf hardwoods in northern Wisconsin and Upper Michigan. injury from high insolation, and phenological be- USDA Forest Service, Research Paper NC-160. North havior. Central Forest Experiment Station, St. Paul, MN. 16 p. Most of the genetic work in sugar maple is current- 13. Carmean, Willard H. 1979. Site index comparisons among ly confined to improving (27) and northern hardwoods in northern Wisconsin and Upper developing ornamental trees (49,62,119). Nur- Michigan. USDA Forest Service, Research Paper NC-169. serymen rely mostly on budding and some grafting North Central Forest Experiment Station, St. Paul, MN. for vegetative propagation. Birds-eye grain trees 17 p. have been grafted since the early 1960’s but results 14. Church, Thomas W., Jr., and R. M. Godman. 1966. The are not available for propagation of this charac- formation and development of dormant buds in sugar teristic (63). The USDA Forest Service, in recent maple. Forest Science 12(3):301-306. 15. Crow, Thomas R., Rodney D. Jacobs, Robert R. Oberg, and work, has selected 228 superior sugar maple trees Carl H. Tubbs. 1981. Stocking and structure for maximum and established three with 126 families growth in sugar maple selection stands. USDA Forest (43). Service, Research Paper NC-199. North Central Forest Hyrbids have been reported between sugar maple Experiment Station, St. Paul, MN. 16 p. and black and red maples (30). Hybrid seedlings 16. Cunningham, Frank E., and Richard J. Peterson. 1965. have been obtained by pollinating sugar maple with Air-layering sugar maple. USDA Forest Service, Research another maple (presumably ) (30). Paper NE-42. Northeastern Forest Experiment Station, Upper Darby, PA. 16 p. 17. Curtis, Robert O., and Boyd W. Post. 1962. Site index Literature Cited curves for even-aged northern hardwoods in the Green Mountains of Vermont. Vermont Agriculture Experiment 1. American Forestry Association. 1982. National register of Station, Bulletin 629. Burlington. 11 p. big trees. American Forests 88(4):36. 18. Erdmann, Gayne G., and Robert R. Oberg. 1973. Fifteen- 2. Anderson, Robert L., and Daniel J. Mosher. 1978. How to year results from six cutting methods in second-growth identify and control Nectria canker. USDA Forest Service, northern hardwoods. USDA Forest Service, Research Paper Northeastern Area State and Private Forestry, Broomall, NC-100. North Central Forest Experiment Station, St. PA. 4 p. Paul, MN. 12 p.

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19. Erdmann, Gayne G., and Robert R. Oberg. 1974. Sapsucker 37. Godman, Richard M., and Gilbert A. Mattson. 1976. Seed feeding damages crown-released yellow birch trees. Journal crops and regeneration problems of 19 species in of Forestry 72 (12):760-763. northeastern Wisconsin. USDA Forest Service, Research 20. Eyre, F. H., ed. 1980. Forest cover types of United States Paper NC-123. North Central Forest Experiment Station, and Canada. Society of American Foresters, Washington, St. Paul, MN. 5 p. DC. 148 p. 38. Godman, R. M., and G. A. Mattson. 1980. Low temperatures 21. Farrington, R. A., and M. Howard, Jr. 1958. Soil optimum for field germination of northern red oak. Tree productivity for hardwood forests of Vermont. In Planters’ Notes 31(2):32-34. Proceedings, First North American Forest Soils Conference. 39. Godman, Richard M., and G. A. Mattson. 1981. Optimum p. 102-109. Michigan State University Agriculture germination temperatures for hardwoods. USDA Forest Experiment Station, East Lansing, MI. Service, Hardwood Management Note. North Central Forest 22. Fayle, D. C. F. 1964. Layering habit of the sugar maple. Experiment Station, St. Paul, MN. 2 p. Forest Chronicle 40(1):116-121. 40. Godman, R. M., and G. A. Mattson. 1981. Thirty-two years 23. Fayle, D. C. F. 1965. Rooting habit of sugar maple and of forest tree seed crop records in northeast Wisconsin. Data yellow birch. Canada Department of Forestry, Publication on file at Rhinelander, WI. 1120. Ottawa, ON. 31 p. 41. Godman, Richard M., and Joseph J. Mendel. 1978. 24. Fisher, R. F., R. A. Woods, and H. R. Glavic. 1978. Economic values for growth and grade changes of sugar Allelopathic effects of goldenrod and aster on young sugar maple in the Lake States. USDA Forest Service, Research Paper NC-155. North Central Forest Experiment Station, maple. Canadian Journal of Forest Research 8(11:1-g. St. Paul, MN. 16 p. 25. Frothingham, E. H. 1915. The northern hardwood forest: its composition, growth and management. U.S. Department of 42. Godman, Richard M., and Carl H. Tubbs. 1973. Establishing even-age northern hardwood regeneration by Agriculture, Bulletin 285. Washington, DC. 79 p. the shelterwood method-a preliminary guide. USDA 26. Gabriel, W. J. 1962. Inbreeding experiments in sugar maple Forest Service, Research Paper NC-99. North Central (Acer saccharum Marsh.)-early results. In Proceedings, Forest Experiment Station, St. Paul, MN. 9 p. Ninth Northeastern Forest Tree Improvement Conference. 43. Gould, Norman E. 1979. Reforestation and timber stand p. 8-12. improvement report for Fiscal Year 1978 and 1979. 27. Gabriel, W. J. 1975. Phenotypic selection of sugar maples WO-2490 Records and Report. USDA Forest Service, for superior sap volume production. In Proceedings, Washington, DC. 57 p. Twenty-first Northeastern Forest Tree Improvement 44. Griffin, H. D. 1965. Maple dieback in Ontario. Forestry Conference. p. 91-96. Chronicle 41(3):295-300. 28. Gabriel, W. J. 1981. Personal communication. 45. Grisez, Ted J. 1975. Flowering and seed production in seven 29. Gevorkiantz, S. R., and William A. Duerr. 1937. A yield hardwood species. USDA Forest Service, Research Paper table for northern hardwoods in the Lake States. Journal of NE-315. Northeastern Forest Experiment Station, Upper Forestry 35:340-343. Darby, PA. 8 p. 30. Godman, R. M. 1965. Sugar maple (Acer saccharum 46. Hawes, F. F., and B. A. Chandler. 1914. The management of Marsh.). In Silvics of forest trees of the United States. p. second growth hardwoods in Vermont. Vermont Agriculture 66-73. H. A. Fowells, camp. U.S. Department of Experiment Station, Bulletin 176. University of Vermont, Agriculture, Agriculture Handbook 271. Washington, DC. Burlington. 88 p. 31. Godman, Richard M. 1969. Culture of young stands. In 47. Hesterberg, G. A. 1957. Deterioration of sugar maple Proceedings, Sugar Maple Conference, August 1969, following logging damage. USDA Forest Service, Station Houghton, MI. p. 82-87. Michigan Technological University Paper 51. Lake States Forest Experiment Station, St. Paul, and USDA Forest Service. MN. 58 p. 32. Godman, Richard M. 1981. Unpublished data. 48. Hibben, C. R. 1962. Investigations of sugar maple decline in 33. Godman, Richard M., and David J. Books. 1971. Influence New York woodlands. Thesis (Ph.D.), Cornell University, of stand density on stem quality in pole-size northern Ithaca, NY. 307 p. hardwoods. USDA Forest Service, Research Paper NC-54. 49. Howe, G. E. 1968. Early results of a sugar maple North Central Forest Experiment Station, St. Paul, MN. provenance study. In Proceedings, Sixteenth Northeastern 7 P. Forest Tree Improvement Conference. p. 27-28. 34. Godman, R. M., and G. A. Mattson. Undated. Relative 50. Jacobs, Rodney D. 1965. Seasonal height growth patterns of tolerance of hardwood and associated seedlings. sugar maple, yellow birch, and red maple seedlings in USDA Forest Service, Hardwood Management Note. North Upper Michigan. USDA Forest Service, Research Note Central Forest Experiment Station, St. Paul, MN. 2 p. LS-57. Lake States Forest Experiment Station, St. Paul, 35. Godman, R. M., and G. A. Mattson. 1970. Periodic growth of MN. 4 p. hardwood influenced by cold weather. Journal of Forestry 51. Jacobs, Rodney D. 1969. Growth and development of deer 68:86-87. browsed sugar maple seedlings. Journal of Forestry 36. Godman, R. M., and G. A. Mattson. 1970. The sprouting 67(12):870-874. potential of dormant buds on the bole of pole-size sugar 52. Jacobs, Rodney D., 1974. Damage to northern hardwood maple. USDA Forest Service, Research Note NC-88. North reproduction during removal of shelterwood overstory. Central Forest Experiment Station, St. Paul, MN. 4 p. Journal of Forestry 72(10):654-656.

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53. Kallio, Edwin, and Carl H. Tubbs. 1980. Sugar maple: an 71. Logan, K. T. 1965. Growth of tree seedlings as affected by American wood. USDA Forest Service, FS-246. Wash- light intensity. I. White birch, yellow birch, sugar maple, ington, DC. 5 p. and silver maple. Canadian Forestry Service, Department of 54. Kelty, Matthew J., and Ralph D. Nyland. 1981. Forests, Publication 1121. Ottawa, ON. 16 p. Regenerating Adirondack northern hardwoods by shelterwood 72. McClenahen, James R. 1978. Community changes in a cutting and control of deer density. Journal of Forestry deciduous forest exposed to air pollution. Canadian Journal 79(1):22-26. of Forest Research 8(4):432-438. 55. Kessler, Kenneth J., Jr. 1969. A basal stem canker of sugar 73. Marquis, David A. 1975. Seed storage and germination maple. USDA Forest Service, Research Note NC-76. North under northern hardwood forests. Canadian Journal of Central Forest Experiment Station, St. Paul, MN. 2 p. Forest Research 5:478-484. 56. Kessler, Kenneth J., Jr. 1972. Sapstreak disease of sugar 74. Marvin, J. W., Mariafranca Morsehi, and F. M. Laing. 1967. maple. USDA Forest Service, Forest Pest Leaflet 128. A correlation between sugar concentration and volume Washington, DC. 4 p. yields in sugar maple-an 18-year study. Forest Science 57. Kessler, Kenneth J., Jr. 1972. Sapstreak disease of sugar 13(4):346-351. maple found in Wisconsin for the first time. USDA Forest 75. Meteer, James W. 1969. Hardwood tree evaluation. In Service, Research Note NC-140. North Central Forest Proceedings, Sugar Maple Conference, August 1969, Experiment Station, St. Paul, MN. 2 p. Houghton, MI. p. 104-111. Michigan Technological 58. Kessler, Kenneth J., Jr. 1974. Annual canker of sugar University and USDA Forest Service. maple in northeastern . Plant Disease Reporter 76. Metzger, Frederick T. 1977. Sugar maple and yellow birch 58(11):1042-1043. seedling growth after simulated browsing. USDA Forest 59. Kessler, Kenneth J., Jr., and John H. Ohman. 1967. Service, Research Paper NC-140. North Central Forest Sunscald canker of sugar maple. Phytopathology 57(8):817. Experiment Station, St. Paul, MN. 6 p. 60. Kliejunas, John T., and James E. Kuntz. 1974. Eutypella 77. Miller, William E., Kenneth J. Kessler, Jr., John H. Ohman, canker, characteristics and control. Forestry Chronicle and John T. Eschle. 1978. Timber quality of northern 50(3):106-108. hardwood regrowth in the Lake States. Forest Science 24(2):247-259. 61. Knight, Fred B. 1969. Insect enemies. In Proceedings, Sugar North Central Forest Experiment Station. 1981. Data on Maple Conference, August 1969, Houghton, MI. p. 32-36. 78. Michigan Technological University and USDA Forest file. Service. 79. Nyland, Ralph D., and William J. Gabriel. 1971. Logging damage to partially cut hardwood stand in New York State. 62. Kriebel, Howard B. 1976. Twenty-year survival and growth AFRI Research Report 5. State University of New York, of sugar maple in seed source tests. Ohio Agriculture Syracuse. 38 p, Research and Development Center, Research Circular 206. 80. Ohman, John H. 1969. Disease. In Proceedings, Sugar University of Ohio, Wooster. Maple Conference, August 1969, Houghton, MI. p. 37-51. 63. Kriebel, H. B. 1981. Personal communication. Michigan Technological University and USDA Forest 64. Kriebel, H. B., and W. J. Gabriel. 1969. Genetics of sugar Service. maple. USDA Forest Service, Research Paper WO-7. 81. Ohman, John H. 1970. Value loss from skidding wounds in Washington, DC. 17 p. sugar maple and yellow birch. Journal of Forestry 65. Kulman, H. M. 1965. Effects of disbudding on the shoot 68(4):226-230. mortality, growth and bud production in red and sugar 82. Ohman, John H., and Kenneth J. Kessler, Jr. 1964. Black maple. Journal of Economic Entomology 58:23-26. bark as an indicator of bird peck defect in sugar maple. 66. Kulman, H. M. 1967. Biology of the hard maple bud miner, USDA Forest Service, Research Paper LS-14. Lake States Obrussa ochrefasciella, and notes on its damage Forest Experiment Station, St. Paul, MN. 8 p. (:Nepticulidae). Annals of the Entomological 83. Ohman, John H., and Kenneth J. Kessler, Jr. 1969. How to Society of America 60:387-391. prevent maple bark diseases. USDA Forest Service, Leaflet 67. Lancaster, Kenneth F., Russell S. Walters, Frederick M. 9. North Central Forest Experiment Station, St. Paul, MN. Laing, and Raymond T. Foulds. 1974. A silvicultural guide 4 P. for developing a sugarbush. USDA Forest Service, Research 84. Ohman, John H., Kenneth J. Kessler, Jr., and G. C. Meyer. Paper NE-286. Northeastern Forest Experiment Station, 1969. Control of Cryptostroma corticale on stored sugar Upper Darby, PA. 11 p. maple pulpwood. Phytopathology 59(6):871-873. 68. Leak, W. B. 1975. Age distribution in virgin red spruce and 85. Olson, David F., Jr., and W. J. Gabriel. 1974. Acer L. Maple. northern hardwoods. Ecology 56(6):1451-1454. In Seeds of woody plants in the United States. p. 187-194. 69. Leak, W. B. 1978. Relationship of species and site index to C. S. Schopmeyer, tech. coord. U.S. Department of habitat in the White Mountains of New Hampshire. USDA Agriculture, Agriculture Handbook 450. Washington, DC. Forest Service, Research Paper NE-397. Northeastern 86. Perala, Donald A. 1974. Growth and survival of northern Forest Experiment Station, Broomall, PA. 9 p. hardwood sprouts after burning. USDA Forest Service, 70. Leak, William B., Dale S. Solomon, and Stanley M. Filip. Research Note NC-176. North Central Forest Experiment 1969. A silvicultural guide for northern hardwoods in the Station, St. Paul, MN. 4 p. Northeast. USDA Forest Service, Research Paper NE-143. 87. Pomerleau, R. 1946. Occurrence and importance of canker Northeastern Forest Experiment Station, Upper Darby, PA. and rots in deciduous forests in Quebec. Phytopathology 34 p. 36:408.

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88. Powell, Douglas S., and E. H. Tryon. 1979. Sprouting ability 105. Trimble, George R., Jr. 1965. Improvement in butt-log of advance growth in undisturbed stands. Canadian Journal grade with increase in tree size, for six hardwood species. of Forest Research 9(1):116-120. USDA Forest Service, Research Paper NE-31. Northeastern 89. Rudolph, V. J., A. K. Quinkert, and J. N. Bright. 1964. Forest Experiment Station, Upper Darby, PA. 15 p. Analysis of growth and stem quality in mixed hardwood 106. Trimble, George R., Jr. 1967. Diameter increase in plantings. Michigan Agricultural Experiment Station, East second-growth Appalachian hardwood stands-a comparison Lansing. Quarterly Bulletin 47(1):94-112. of species. USDA Forest Service, Research Note NE-75. 90. Rushmore, Francis M. 1969. Sapsucker damage varies with Northeastern Forest Experiment Station, Upper Darby, PA. tree species and seasons. USDA Forest Service, Research 5 P. Paper NE-136. Northeastern Forest Experiment Station, 107. Trimble, George R., Jr. 1973. The regeneration of central Upper Darby, PA. 19 p. Appalachian hardwoods with emphasis on the effects of site 91. Shetron, S. G. 1972. Site index curves for sugar maple in quality and harvesting practice. USDA Forest Service, northern Lower Michigan. Michigan Technological University, Research Paper NE-282. Northeastern Forest Experiment Research Note 6. Houghton. 8 p. Station, Upper Darby, PA. 14 p. 92. Shigo, Alex L. 1963. Ring shake associated with sapsucker 108. Tubbs, Carl H. 1965. Influence of temperature and early injury. USDA Forest Service, Research Paper NE-8 spring conditions on sugar maple and yellow birch Northeastern Forest Experiment Station, Upper Darby, PA. germination in Upper Michigan. USDA Forest Service, 10 p. Research Note LS-72. Lake States Forest Experiment 93. Shigo, Alex L. 1965. Organism interactions in decay and Station, St. Paul, MN. 2 p. discoloration in beech, birch, and maple. USDA Forest 109. Tubbs, Carl H. 1968. The influence of residual stand Service, Research Paper NE43. Northeastern Forest densities on regeneration in sugar maple stands. USDA Experiment Station, Upper Darby, PA 24 p. Forest Service, Research Note NC-47. North Central Forest 94. Shigo, Alex L., and Edwin vH. Larson. 1969. A photoguide Experiment Station, St. Paul, MN. 4 p. to the patterns of discoloration and decay in living northern 110. Tubbs, Carl H. 1973. Allelopathic relationships between hardwood trees. USDA Forest Service, Research Paper yellow birch and sugar maple seedlings. Forest Science NE-127. Northeastern Forest Experiment Station, Upper 19(2):139-145. Darby, PA. 100 p. 111. Tubbs, Carl H. 1977. Age and structure of a northern hardwood selection forest, 1929-1976. Journal of Forestry 95. Shigo, Alex L., William B. Leak, and Stanley M. Filip. 1973. Sugar maple borer injury in four hardwood stands in New 75(1):22-24. Hampshire. Canadian Journal of Forest Research 112. Tubbs, Carl H., and Louis J. Verme. 1972. How to create 3(4):512-515. wildlife openings in northern hardwoods. USDA Forest Service, North Central Forest Experiment Station, St. Paul, 96. Shortle, W. C., J. B. Kotheimer, and A. E. Rich. 1972. Effect MN. 5 p. of salt injury on shoot growth of sugar maple, Acer Plant Disease Reporter 56(11):1004-1007. 113. U.S. Department of Agriculture, Forest Service. 1964. The saccharum. causes of maple blight in the Lake States. USDA Forest 97. Siccama, Thomas G. 1974. Vegetation, soil and climate on Service, Research Paper LS-10. Lake States Forest the Green Mountains of Vermont. Ecological Monographs Experiment Station, St. Paul, MN. 15 p, 44(3):325-349. 114. Von Althen, F. W. 1977. Planting sugar maple; fourth-year 98. Simmons, Gary A., and Fred B. Knight. 1973. Deformity of results of an experiment on two sites with eight soil sugar maple caused by bud feeding insects. Canadian amendments and three weed control treatments. Canadian Entomologist 1051559-1566. Forestry Service, Department of Fisheries and Environment, 99. Solomon, Dale S., and Barton M. Blum. 1967. Stump Report O-X-257. Sault Ste. Marie, ON. 10 p. sprouting of four northern hardwoods. USDA Forest 115. Wang, B. S. P. 1974. Tree-seed storage. Canadian Forestry Service, Research Paper NE-59. Northeastern Forest Service, Department of Environment, Publication 1335. Experiment Station, Upper Darby, PA. 13 p. Ottawa, ON. 32 p. 100. Stearns, Forest W. 1969. Wildlife pressures. In Proceedings, 116. Ward, James C., and Richard M. Marden. 1965. Sugar Sugar Maple Conference, August 1969, Houghton, MI. p. maple veneer logs should be graded for pith flakes. USDA 51-59. Michigan Technological University and USDA Forest Service, Research Note LS41. Lake States Forest Forest Service. Experiment Station, St. Paul, MN. 4 p. 101. Stoeckeler, J. H., and G. W. Jones. 1957. Forest nursery 117. Ward, W. W., J. V. Berglund, and F. Y. Borden. 1966. practice in the Lake States. U.S. Department of Agriculture, Soil-site characteristics and occurrence of sugar maple Agriculture Handbook 110. Washington, DC. 124 p. canker in Pennsylvania. Ecology 47(4):541-548. 102. Stone, Douglas M. 1977. Fertilizing and thinning northern 118. Webb, D. Paul. 1976. Root growth in Acer saccharum hardwoods in the Lake States. USDA Forest Service, Marsh. seedlings: effects of light intensity and photoperiod Research Paper NC-141. North Central Forest Experiment on root elongation rates. Botanical Gazette 137(3):211-217. Station, St. Paul, MN. 7 p. 119. Wendel, G. W., and W. J. Gabriel. 1976. Sugar maple 103. Stone, Douglas M. 1977. Leaf dispersal in a pole-size maple provenance study: outplanting 6-year results. stand. Canadian Journal of Forest Research 7(1):189-192. In Proceedings, Twenty-second Northeastern Forest Tree 104. Taylor, F. H. 1956. Variation in sugar content of maple sap. Improvement Conference, 1974. p. 163-171. Vermont Agriculture Experiment Station, Bulletin 587. 120. Westing, A. H. 1966. Sugar maple decline: an evaluation. University of Vermont, Burlington. 39 p. Economic Botany 20(2):196-212.

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121. Williams, Robert D., and Sidney H. Hanks. 1976. Hardwood 126. Yawney, Harry W., and Clayton M. Carl, Jr. 1968. Sugar nurseryman’s guide. U.S. Department of Agriculture, maple seed research. In Proceedings, Twentieth Anniversary Agriculture Handbook 473. Washington, DC. 78 p. Nurserymen’s Conference, September 1968, Delaware, OH. 122. Winget, Carl H. 1969. Apparent defect in second-growth p. 115-123. USDA Forest Service, Northeastern Area State tolerant hardwood stands in Quebec. Forestry Chronicle and Private Forestry, Upper Darby, PA. 45(3):180-183. 127. Yawney, Harry W., and Clayton M. Carl, Jr. 1970. A sugar 123. Witter, J. A., and R. D. Fields. 1977. Phyllobius oblongus maple planting study in Vermont. USDA Forest Service, and Sciaphillus asperatus associated with sugar maple Research Paper NE-175. Northeastern Forest Experiment reproduction in northern Michigan. Environmental Station, Upper Darby, PA. 14 p. Entomology 6(1):150-X4. 128. Yawney, Harry W., and J. R. Donnelly. 1981. Clonal 124. Yawney, Harry W. 1969. Artificial regeneration. In propagation of sugar maple by rooting cuttings. In Proceedings, Sugar Maple Conference, August 1969, Proceedings, Twenty-seventh Northeastern Forest Tree Houghton, MI. p. 65-74. Michigan Technological University Improvement Conference, 1979. p. 72-81. and USDA Forest Service. 129. Yawney, Harry W., and J. R. Donnelly. 1982. The vegetative 125. Yawney, Harry W. 1976. The effects of four levels of shade propagation of sugar maple. In Summary of Sugar Maple in sugar maple seedling development. (Abstract) In Research at the George D. Aiken Laboratory. Chapter 9, p. Proceedings, Fourth North American Forest Biology 61-70. USDA Forest Service, General Technical Report Workshop. p. 189-190. State University of New York, NE-72. Northeastern Forest Experiment Station, Broomall, College of Environmental Science and Forestry, Syracuse. PA.